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points by ahartmetz 1 day ago | 0 comments

LLVM was supposed to be a virtual machine initially, hence the (original) name: Low-level virtual machine. The direction that it took, and especially the development of Clang: that was at least partially because of GCC's intentional anti-modularity.

[–] jcranmer 1 day ago

LLVM was never meant to be a virtual machine, which is the reason why its name was ultimately changed. (It's closer to an instantiation of the C abstract machine, which is where the "virtual machine" came from.)

[–] ahartmetz 1 day ago

AFAIK, being a flexible JIT compiler (for C-like languages, not Java) was a large part of the idea. The pivot to static compilation only happened "accidentally" in the first few years until the by then pretty broken JIT part was officially removed. Correct me if I'm wrong.

[–] jcranmer 16 hours ago

You're wrong. See e.g. https://llvm.org/pubs/2002-12-LattnerMSThesis.pdf, the original thesis proposing LLVM.

LLVM was always trying to pitch itself as a whole-lifetime optimization system. In practice, this meant focusing on LTO and PGO compilation modes. The idea of runtime or idle-time optimization were always kind of a next-todo step rather than anything actually implemented.